Steel or Aluminuim for Motor Mount

[KawaSpark]

Hi Guys

I am about to get the metal cut for SepEx motor. What I don't know is how do I choose between Steel or Aluminum.

And more important what thickness will with stand the torque? I was thinking 10mm should be more than sufficient but that is guessing.

Thanks In advance.

[teddillard]

How is it attaching to the frame? Is it welded or bolted?

If it's welded, it's simple- use the same material as the frame. If you're bolting, I'm not sure it makes much difference. The weight difference isn't enough to justify aluminum, I used steel because the guy doing my water-jet cutting could work it into the ticket easier. If you're cutting it yourself, aluminum is certainly easier.

On the torque issue- wars have been fought over less, but my personal opinion is that there is far less strain on the mount that you'd suspect. I did a post on the subject, but I did a really slap-dash job to get the bike on the road for some real testing, and after seeing how robust my mount really was, I let it go as it was. It was 1/4" steel, and I'll be beefing it up this winter, but still- it works great.

That post is here:
http://evmc2.wordpress.com/2010/09/11/the-motor-mount/

[frodus]

do you have a design?

You could chose 1/4" thick steel and have it fail depending on the structure..... so it all kinda depends.

[ZoomSmith]

The time to choose the material is before you design the structure.
Every material has different properties to design around, but my rule of thumb is the aluminunum will need to be 50% thicker than steel.

[frodus]

Zoom,
Yeah, he said he's sending it to get cut..... so I'm assuming he must already have a design in mind.... probably not a great idea to chose materia after the fact.

You can have a 1/4" thick Aluminum plate design be a very rigid structure, more rigid than a differently designed 3/8" design. It all depends on how its supported/structured. So yeah, chosing the metal before design will help in your design.